Reset converter state after second wchar_t output (Bug 25734)

An input BIG5-HKSCS character may be converted into at most 2 wchar_t
characters. After outputting the second whcar_t character (which was
saved in the converter state) we must reset the state. If we fail
to reset the state we will be stuck continually copying that
character to the output even if we have further input to consider.

We add a new test case that covers the 4 BIG5-HKSCS characters
that may become 2 wchar_t characters.

Reviewed-by: Tom Honermann <tom@honermann.net>

3 files changed, 176 insertions, 4 deletions

diff --git a/iconvdata/Makefile b/iconvdata/Makefile
index c83962f351..4ec2741cdc 100644
--- a/iconvdata/Makefile
+++ b/iconvdata/Makefile
@@ -73,7 +73,7 @@ modules.so := $(addsuffix .so, $(modules))
 ifeq (yes,$(build-shared))
 tests = bug-iconv1 bug-iconv2 tst-loading tst-e2big tst-iconv4 bug-iconv4 \
 	tst-iconv6 bug-iconv5 bug-iconv6 tst-iconv7 bug-iconv8 bug-iconv9 \
-	bug-iconv10 bug-iconv11 bug-iconv12
+	bug-iconv10 bug-iconv11 bug-iconv12 tst-iconv-big5-hkscs-to-2ucs4
 ifeq ($(have-thread-library),yes)
 tests += bug-iconv3
 endif
@@ -275,16 +275,21 @@ endif
 endif
 endif
 
-include ../Rules
-
 ifeq ($(run-built-tests),yes)
-LOCALES := de_DE.UTF-8
+LOCALES := \
+	de_DE.UTF-8 \
+	zh_HK.BIG5-HKSCS \
+	$(NULL)
+
 include ../gen-locales.mk
 
 $(objpfx)bug-iconv6.out: $(gen-locales)
 $(objpfx)tst-iconv7.out: $(gen-locales)
+$(objpfx)tst-iconv-big5-hkscs-to-2ucs4.out: $(gen-locales)
 endif
 
+include ../Rules
+
 # Set libof-* for each routine.
 cpp-srcs-left := $(modules) $(generated-modules) $(libJIS-routines) \
 		 $(libKSC-routines) $(libGB-routines) $(libCNS-routines) \
@@ -340,3 +345,7 @@ tst-tables-clean:
 
 $(objpfx)gconv-modules: gconv-modules
 	cat $(sysdeps-gconv-modules) $^ > $@
+
+# Test requires BIG5HKSCS.
+$(objpfx)tst-iconv-big5-hkscs-to-2ucs4.out: $(objpfx)gconv-modules \
+			 $(addprefix $(objpfx),$(modules.so))
diff --git a/iconvdata/big5hkscs.c b/iconvdata/big5hkscs.c
index 01fcfeba76..ef325119b1 100644
--- a/iconvdata/big5hkscs.c
+++ b/iconvdata/big5hkscs.c
@@ -17895,6 +17895,9 @@ static struct
 	else								      \
 	  ++inptr;							      \
       }									      \
+    else								      \
+      /* Clear the queue and proceed to output the saved character.  */	      \
+      *statep = 0;							      \
 									      \
     put32 (outptr, ch);							      \
     outptr += 4;							      \
diff --git a/iconvdata/tst-iconv-big5-hkscs-to-2ucs4.c b/iconvdata/tst-iconv-big5-hkscs-to-2ucs4.c
new file mode 100644
index 0000000000..8389adebf2
--- /dev/null
+++ b/iconvdata/tst-iconv-big5-hkscs-to-2ucs4.c
@@ -0,0 +1,160 @@
+/* Verify the BIG5HKSCS outputs that generate 2 wchar_t's (Bug 25734).
+   Copyright (C) 2020 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <stdio.h>
+#include <string.h>
+#include <locale.h>
+#include <wchar.h>
+#include <support/check.h>
+#include <support/support.h>
+
+/* A few BIG5-HKSCS characters map in two unicode code points.
+   They are:
+   /x88/x62 => <U00CA><U0304>
+   /x88/x64 => <U00CA><U030C>
+   /x88/xa3 => <U00EA><U0304>
+   /x88/xa5 => <U00EA><U030C>
+   Each of these is special cased in iconvdata/big5hkscs.c.
+   This test ensures that we correctly reset the shift state after
+   outputting any of these characters.  We do this by converting
+   each them followed by converting an ASCII character.  If we fail
+   to reset the shift state (bug 25734) then we'll see the last
+   character in the queue output again.  */
+
+/* Each test has  name, input bytes, and expected wide character
+   output.  */
+struct testdata {
+  const char *name;
+  const char input[3];
+  wchar_t expected[3];
+};
+
+/* In BIG5-HKSCS (2008) there are 4 characters that generate multiple
+   wide characters.  */
+struct testdata tests[4] = {
+  /* <H-8862>X => <U+00CA><U+0304>X */
+  { "<H-8862>", "\x88\x62\x58", { 0x00CA, 0x0304, 0x0058 } },
+  /* <H-8864>X => <U+00CA><U+030C>X */
+  { "<H-8864>", "\x88\x64\x58", { 0x00CA, 0x030C, 0x0058 } },
+  /* <H-88A3>X => <U+00EA><U+0304>X */
+  { "<H-88A3>", "\x88\xa3\x58", { 0x00EA, 0x0304, 0x0058 } },
+  /* <H-88A5>X => <U+00EA><U+030C>X */
+  { "<H-88A5>", "\x88\xa5\x58", { 0x00EA, 0x030C, 0x0058 } }
+};
+
+/* Each test is of the form:
+   - Translate first code sequence (two bytes)
+   - Translate second (zero bytes)
+   - Translate the third (one byte).  */
+static int
+check_conversion (struct testdata test)
+{
+  int err = 0;
+  wchar_t wc;
+  mbstate_t st;
+  size_t ret;
+  const char *mbs = test.input;
+  int consumed = 0;
+  /* Input is always 3 bytes long.  */
+  int inlen = 3;
+
+  memset (&st, 0, sizeof (st));
+  /* First conversion: Consumes first 2 bytes.  */
+  ret = mbrtowc (&wc, mbs, inlen - consumed, &st); 
+  if (ret != 2)
+    {
+      printf ("error: First conversion consumed only %zd bytes.\n", ret);
+      err++;
+    }
+  /* Advance the two consumed bytes.  */
+  mbs += ret;
+  consumed += ret;
+  if (wc != test.expected[0])
+    {
+      printf ("error: Result of first conversion was wrong.\n");
+      err++;
+    }
+  /* Second conversion: Consumes 0 bytes.  */
+  ret = mbrtowc (&wc, mbs, inlen - consumed, &st); 
+  if (ret != 0)
+    {
+      printf ("error: Second conversion consumed only %zd bytes.\n", ret);
+      err++;
+    }
+  /* Advance the zero consumed bytes.  */
+  mbs += ret;
+  consumed += ret;
+  if (wc != test.expected[1])
+    {
+      printf ("error: Result of second conversion was wrong.\n");
+      err++;
+    }
+  /* After the second conversion the state of the converter should be
+     in the initial state.  It is in the initial state because the two
+     input BIG5-HKSCS bytes have been consumed and the 2 wchar_t's have
+     been output.  */
+  if (mbsinit (&st) == 0)
+    {
+      printf ("error: Converter not in initial state.\n");
+      err++;
+    }
+  /* Third conversion: Consumes 1 byte (it's an ASCII character).  */
+  ret = mbrtowc (&wc, mbs, inlen - consumed, &st); 
+  if (ret != 1)
+    {
+      printf ("error: Third conversion consumed only %zd bytes.\n", ret);
+      err++;
+    }
+  /* Advance the one byte.  */
+  mbs += ret;
+  consumed += ret;
+  if (wc != test.expected[2])
+    {
+      printf ("error: Result of third conversion was wrong.\n");
+      err++;
+    }
+  /* Return 0 if we saw no errors.  */
+  return err;
+}
+
+static int
+do_test (void)
+{
+  int err = 0;
+  int ret;
+  /* Testing BIG5-HKSCS.  */
+  xsetlocale (LC_ALL, "zh_HK.BIG5-HKSCS");
+
+  /* Run all the special conversions.  */
+  for (int i = 0; i < (sizeof (tests) / sizeof (struct testdata)); i++)
+    {
+      printf ("Running test for %s\n", tests[i].name);
+      ret = check_conversion (tests[i]);
+      if (ret > 0)
+	printf ("Test %s failed.\n", tests[i].name);
+      err += ret;
+    }
+
+  /* Fail if any conversion had an error.  */
+  if (err > 0)
+    FAIL_EXIT1 ("One or more conversions failed.");
+
+  return 0; 
+}
+
+#include <support/test-driver.c>